Multiple-access communication systems utilizing noise coded signals are well known and are particularly desirable because they exhibit an immunity against self-interference and jamming. Noise coded means that the information is coded with a code that is "noise like" in that it will compress to an impulse upon autocorrelation. In particular, one class of noise codes are known wherein pairs of coded signals termed "code mates" have amplitudes and autocorrelation functions which provide a peak output at a given time and a zero output or outputs having the same magnitude but opposite polarity at all other times. When the code mates, for example, are multiplexed, matched filter detected and linearly added, there is provided a lobeless impulse output of a relatively high amplitude at a given time (.tau.=0) and a zero output at all other times. Such codes and systems utilizing such codes are typically shown and described in U.S. Pat. No. 3,461,451, entitled, "Code Generator To Produce Permutations Of Code Mates", which issued to F. S. Gutleber, the present inventor, on Aug. 12, 1969; U.S. Pat. No. 3,634,765, entitled, "System To Provide An Impulse Autocorrelation Function . . . Of One Or More Of Said Code Signals", issued to F. S. Gutleber on Jan. 11, 1972; and U.S. Pat. No. 3,908,088, entitled, "Time Division Multiple Access Communications System", issued to F. S. Gutleber on Sept. 23, 1975. The teachings of these patents are herein meant to be incorporated specifically by reference. This application is also related to applicants co-pending application Ser. No. 402,476, filed July 28, 1982, entitled Multiplexed Noise Coded Switching System.
In a more recent patent by the subject inventor, identified as U.S. Pat. No. 4,301,530, entitled, "Orthogonal Spread Spectrum Time Division Multiple Accessing Mobile Subscriber Access System", which issued on Nov. 17, 1981, there is disclosed a system employing multiplexed noise codes of the type referred to above wherein a central node, or repeater, is utilized between a plurality of users desiring to communicate with one another with transmissions to the central node being performed at a first frequency and with retransmissions from the central node being performed at a second, different frequency; however, all the users employ the same code mate pairs but different available time slots within a channel frame period. The teachings of this patent are also meant to be incorporated herein by reference since it provides a basis for the subject invention which will be hereinafter described.
Furthermore, the utilization of different noise codes for a plurality of users, for example, in a mobile subscriber multiple-access system, normally results in non-orthogonal operation, meaning that self-interference is inherent in the system operation. Although each interfering signal is reduced by the time-bandwidth product, interfering users in close proximity are generally intolerable.